A joint role for forced and internally-driven variability in the decadal modulation of global warming
Liguori, G., McGregor, S., Arblaster, J. M., Singh, M. S., & Meehl, G. A. (2020). A joint role for forced and internally-driven variability in the decadal modulation of global warming. Nature Communications, 11, 3827. doi:10.1038/s41467-020-17683-7
Despite the observed monotonic increase in greenhouse-gas concentrations, global mean temperature displays important decadal fluctuations typically attributed to both external forcing and internal variability. Here, we provide a robust quantification of the relative contributions of anthropogenic... Show moreDespite the observed monotonic increase in greenhouse-gas concentrations, global mean temperature displays important decadal fluctuations typically attributed to both external forcing and internal variability. Here, we provide a robust quantification of the relative contributions of anthropogenic, natural, and internally-driven decadal variability of global mean sea surface temperature (GMSST) by using a unique dataset consisting of 30-member large initial-condition ensembles with five Earth System Models (ESM-LE). We present evidence that a large fraction (similar to 29-53%) of the simulated decadal-scale variance in individual time-series of GMSST over 1950-2010 is externally forced and largely linked to the representation of volcanic aerosols. Comparison with the future (2010-2070) period suggests that external forcing provides a source of additional decadal-scale variability in the historical period. Given the unpredictable nature of future volcanic aerosol forcing, it is suggested that a large portion of decadal GMSST variability might not be predictable. Show less